The invention relates to a gas seal for shafts of compressors or other working machines in which operating spaces, in the zone where the shaft passes through a housing, must be hermetically sealed against the ambience and only small amounts of sealing gas can be allowed to penetrate into these operating spaces.
Such shaft seals comprise a sealing ring which is dimensionally stable and rotates with the shaft, and one or two sealing rings which do not rotate with the shaft and are mounted in the housing resiliently and gas-tightly by means of diaphragms and are axially biased to form radial sealing gaps with the rotating sealing ring. The diaphragms and the non-rotating sealing rings may be made of different materials. The gaps must provide boundaries for a sealing gas cushion to meet operating conditions of the machine. The gaps must be very narrow, i.e., have a width in the micron range.
It will be understood that a distortion, by heat, of such sealing rings may very easily lead to a slight grazing of the parts. This may cause severe damage, since the sealing gas has no lubricating capability. This risk is greater the more the thermal expansion of the materials of the component parts connected to one another, differ from each other. For example, a non-rotating sealing ring of aluminum secured to the housing through a steel bellows to obtain a gastight resilient connection, can hardly be employed at temperatures above 80.degree. since at such a temperature the distortion is large enough to cause a contact with the sealing ring rotation with the shaft and forming the other boudary of the radial seal gap.